----- Original Message -----
From: "David McClain" <dmcclain1@mindspring.com>
To: "Xavier Leroy" <Xavier.Leroy@inria.fr>
Sent: Thursday, March 29, 2001 2:34 PM
Subject: Re: [Caml-list] Complex numbers in OCaml


> > As Markus mentioned, I'm considering extending the Bigarray module to
> > handle complex numbers as well.  This would help interfacing with
> > Fortran, and provide essentially the same data representation than in
> > C and Fortran.
>
> If you do this you need to be aware that:
>
> 1. Most C representations use arrays in which real and imaginary parts are
> in adjacent memory addresses, interleaved throughout the entire array, and
>
> 2. Most Fortran representations use separate arrays for the real parts and
> the imaginary parts.
>
> I say "most" based purely on my own personal experiences with all the glue
> code I have had to write to interface to the IMSL, NAG, MatLab, BLAS, and
> MKL code.
>
> My experiments here have shown me that there is a real speed penalty on
> Pentium II and III architectures for the separate array versions of code,
> contrasted with the interleaved structure versions. I can only assume that
> this has to do with data locality and cache performance.
>
> I ultimately gave up trying to come up with a "standard" array
> representation, except within my own little universe. I was quite
surprised
> to find that a data structure as fundamental as an array of numbers can
have
> so many different implementations.
>
> - DM
>

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